Electrical sound translating device



y 23, 1950 y L. B. CORNWELL El AL 2,508,783

.ELECTRICAL SOUND TRANSLATING DEVICE Filed Feb. 16, 1945 Patented May 23, 1950 UNlTEDi STATEdJ"PATENT' OFFICE Lionel B. CornwelLNetv Canaan, Conn., and John Ff. Nielsen, Forest Hills, N. Y.

- Application February 16, 1945, Serial No. 578,206

. 15 Claim-sit. (Cl. 179-10041) This invention relates to electrical sound translating devices of the so-called magnetic type. The invention is useful intranslating mechanical motion into electrical impulses, as well as in translating electrical impulses into mechanical motion.

- The invention is adapted for use as a microphone or to pick up any motion of a vibratory nature. As exemplified in the present embodiment the invention takes the form of a phonoraph pickup and the following disclosure of such embodiment will be suflicientto permit those skilled in the art to understand the invention and the various uses to which it may be put.

In the usualmagnetic'pickup device of the prior art the magnetic forces tend to pull the armature to one pole face or the other and subject the armature to freezing to a pole piece; and'the armature is likewise subject to striking the pole pieces during its operative movement. To prevent this it hasbeen found necessary or desirable to employ rubber'damper blocks. It has been attempted, without success, 'to make these dampers'compliant enough to allow armature vibration within the desired limits of opera tion but stiff enough to oppose the magnetic pull and t'o'normally center the armature in a neutral or mid'position. When' such damper blocks are stiff enough to effect centering of the armature poor fidelity of reproduction results, thereby requiring a'compromise which results in neither a faithful reproduction nor in freedom from freez- 1 ing. Additionally, the necessary stiffness of these blocks imposesupon the stylus an undesirable resistance to lateral motion, causing premature wearing'of the record groove. g

Anotherdisadvantage of the prior art' magnetic pickup devices resides in the fluctuation of density and "reversal of flow of magnetic flux" through the armature each time the stylus is oscillated through acomplete cycle of movement," as by a sound record groove. This is highly'undesirable because of eddy losses and hysteresis which'are appreciable in view of the small mass of the armature and the relative high flux density necessary in order to attain fidelity and high output efficiency of reproduction with the use of an armature having small mass;

In sound track records of the lateral undulation type there are also present slight vertical undulations, andhence it is desirable that a stylus in following the lateral undulations also have a certain degree'of freedom-to follow the 2 lateral undulations and conversel it is desirable to prevent translation of the ancillary vertical vibrations into sound. Similarly, in vertical undulation type records there are also present slight lateral undulations of an ancillary nature and for similar reasons it is desirable to provide some freedom of movement of the stylus laterally while at the same time refraining from translating said ancillary undulations into sound. An object of this invention is to provide a device'which will overcome the above shortcom' ings and disadvantages and which will have the attributes above indicated.

Another objectof theinvention is to provide a device of the type'described which will faithfully translate the desired sound while prohibiting undesirable noises due to extraneous electrical disturibances. V Another object of the invention is to provide a device adapted for universal use with records of either the lateral cut or verticalcut types.

' The invention consists of the novel features, arrangements, construction and combination of parts embodied, by way of example," in the apparatus to be hereinafter morefully described as illustrating a present preferred form of themvention, and the invention willbe more particularly pointed out in the appended claims.

Further and more specific objects, features and along the line 2- -2 of Fig. 1; p v 7 v Fig. 3 is a bottom view of Fig. [showing f r therparticulars as to the mounting of the armature and showing the spacing betWeenthe armature and cooperating pole pieces exaggerated for the purposes of clarity;

Fig, 4 is a fragmentary view of certain parts,

'shown'in Fig. 2, on a somewhat larger scale, to

. illustrate the partsand in a difierent position;

fully reproduce the sound represented by said and Fig. 5 is a diagrammatic view in perspective illustrating a feature of the invention. Before describing the invention in detail certain salient features will be referred to byway of introduction. Animportant feature of the invention resides in the use of a resiliently sup ported magnetic armature that cannot freeze to any of the magnetized poles and which has"unre-' maintenance of a uni-directional flow of flux. through the armature; and the bucking out of undesirable coil currents resulting from extraneous electrical disturbances or due to lateral mot tion of the stylus when reproducing vertical cut records and vice versa.

Referring to the drawings and more particularly to Fig. 1, a magnetic field is provided by a suitable magnet in which is polarized, as shown by the letters N. and S, which in turn polarizes' the laminated. transformer iron pole pieces 2 and 13 having respectively correspondi g branch poles Nl-NZ and. 51-82. The magnet in is. preferably a permanent magnet and is supported on a suitable i-rame such as. H. An armature, designated. in general as l-.4-, isdisposedbetween the poles N ke-N2 and Sl-SZ so. as to completethe flux path or lie therfield of influence O f the flux fiowing between. said poles. It is. noted in this connection thatthe poles. are so disposed asto cause the magnetic flux to flow in the samedirection between the poles N.l;, $I andNZ, S2. The armature L4 hasoppositely disposed. ends; re-

spectively adjacent.poles:Nl-N2 and SL-S2 spatial. interleaved. relationship therewith. In. the present embodiment the armature ends. take the form of two plates providing the end; por-- tions |-5.- 1 and Iii-49 which are respectively spatially interleaved with threeplates provided in the poles- NI.-N2 and three plates provided in.

the poles SI.-S2 Itwillbe. seen. (Figs. 1; 2. and

4-). that the verticalside faces of the. three plates of the Ni pole are disposed in coplanar relationship with. the. respectively cooperating vertical. faces of the. three plates of the N2 poleand-are: spaced verticallytherefrom; and similarlyv (Figs. 1 and 3) the vertical. side faces of the three.

plates of the Si. pole. are disposed. in coplanar relationship with the respectively cooperating. verticalfaces; of the three plates of the S2, poleand are spaced verticallytherefrom. Likewise the said vertical side facesOf the-Ni and'NZ pole plates are coplanar. with. the respectively cooperating verticalsidefaces of. the Si andrSZ-pole plates and are spaced laterally therefrom.. In-

the alternative,.the armature. could be-one piece with bifurcated ends but the illustrated structure ispreferable asthe entire armature mass is magnetically useful. The plate-endsof. the armature:

arespaced onall sides from thecorrespondingly adjacent poleswith a clearanceof. approximately .002" to allow a free motionvertically or. arocking motion aroundan imaginary center 0 as an axis. The mountingof. the armature, to be more.

particularly. described following, and. the. disvaried in accordance with armature movement, but within the limits of operative movement the interleaving relationship is always present. This provides a substantially constant air gap length and a variable air gap area and is one of the important features of the present invention. This principle is diagrammatically illustrated in Fig. 5 wherein a plateiZil is disp'ose'd between a pair of plates 24-2 2 ini spatial interleaved relationship and is adapted for relative movement from the full line position to the dotted line position. As-

suming that magnetic flux is passing between the plate 20 and plates 2l-22, the magnetic air "gap between the plate 20 and the plates 2l22 inadirectionnormal to the plates is constant at all -tiines. Flux modulation is obtained by variation.in-. the area of coupling and is maximum when plate 20 is in the position indicated by the'breken lines and is minimum when the plate 20 is in the position indicated by solid lines. Assuming that with the constant gapof- .002!" the fiuxdensity is 8i000:1i1,ies per sc uareinch andthe: total .fiux area-.invthesolid lineposit-ionto-be .040 square. inch the resultant minimum flux willbe: 32D'1in s p r square inch .How v r,. wi h the plate 29 in the broken line position the-maximum a a of c p i s provided and assumin t to be one square inch, themaximum flux of 8;,000: lines pe s uare nch sprovidedr Variati ns-ble T tween the minimum of .320 lintS nd thermaxi-- mumlofi spec. lines: are obtainedby the variation o th ar a f ouplin T e a matu Wis-h ld n correctpes t n th e p ct he p l -Nlaitand-sl-s bv a flat ribbonisprings.23 ,.the inner end of which-isrigid- 1y secured to:therame Il -and the outer. end-of. which carries. secured thereto the plates which. p e t rm ture I4. A-strlus 24 issuit ably secured to the armature M? for movementtherewith, the: present embodiment the:

stylus,.which 15 12136 means for trans-mittil'lgz mechanical: motion to or irom' the armature, is pro videdlwith a base-24! rigidly secured to -the. spring,. as by riveting. A loop. of. finewire 25 isrloopeda 5 over the tylus. 21L and itsrendsare securely anchored closetogetherto the irame- H to provide a, br e rvin t h th stylus a a nst the fIlClSlQIIEtI'fOlCB createdby therecord as it slidesunder the stylus in the direction indicated by e arrow 1; e 2) thu n rinsmeten ion' ithe stylus in a ver-ticalposition relative. tothe longitudinal directionl) while permitting lateral motion.

The p c p-assembl iaso halanfl d -il' f senta pressuraot a predeterminedrvalue, onithe record. The invention hassbeenssuccessfully op erated with fidelity: of reproductionemploying predetermined pressures at: least as low as 20' gramsand as highat, least. as: 40* grams. The pressure may? be, varied in=acoordance with the record material employed. and the. degree. of external vibrations present; in present-practice (the pressureof. 30. to 35. grarnsfis desirable. pressure wheniapplied; pushes the-armature. into. the positionas shown iii Figures: 2 and 3. putting. the spring under. the: required. tension necessary to overcome: theinertia-of. the armature. and stylus when vibrating, vertically: over the frequencyrange at the maximum: amplitude cutton vertical. records. Devices. made in. accordance withthe invention iunction witha high=degree of uniformity ofresponse and. tests. of. suchdevices produce airequency curve-in the: form otasubstantially straight line with n -drop-oiiof dip in the curve; at the. maximum frequency; which itis commercially possible to record onfrequency; test records at the present time. The tests of this device indicate that the invention is inherently capable of faithfully responding to frequencies far higher andlower than the frequencies which are recordable at the present time. This predetermined tension holds the armature in the same position for lateral operation allowing the. free rocking motion of the armature to take place,

in operation with lateral cut records. The spring 23 is so shaped that its unloaded position is as shown in Fig.4, and when in loaded or operative. position the parts are disposed as shown in Figs.v l, 2 and 3 with the armature in neutral position, both mechanically and electrically. With av thickness of spring to meet. the above require-.

being pulledto either side bodily, thus preventing; contact of the armature I4 with any of the poles.

NI-N2 and SIS2. Accordingly, the stylus 24 is adapted to follow either a vertical or a lateral. cut record and transform the groove undulations into mechanical motion which in turn modulates the magnetic field passing between the poles N IN2 and SI-S2 and through the armature I4.

Two oppositely woundcoils 25, 21, preferably identical in dimension, number of turns, and impedance, surround respectively corresponding; branches of the pole pieces I2 and I3, as shown in'Fig. 1 somewhat diagrammatically. This ar-.

rangement serves to transform the magnetic fluctuations resulting in the movement of the arma-.

ture, into corresponding alternating electrical potentials in the manner to be more particularly pointed out following.

When it is'desired to use the invention for vertical cut records the coil terminals 26b and 21a are connected together, and the coil terminals 26a and 27b are connected to a suitable receiving circuit, such as-iswell known to-those skilled in the art and need not be further described. Assuming a vertical vibratory force to be applied to the stylus, as by the undulations on a vertical cut reccm,- the following magnetic and consequent electrical action takes place. The armature moves upward away from poles NI and SI and toward poles N2 and S2, thus reducing the magnetic flux between the poles NI and SI and increasing the magnetic flux between the poles N 2 and S2'to the same extent due to the fact that the area of over- 7 lap between the armature I4 and the poles NI and SI decreases in the same ratio as the overlap with respectto the poles N2 and S2 increases.

This induces an electrical potential in the coils" 26 and 21. When the armature I4 moves downwardly, the flow of flux between the poles NI and SI is correspondingly increased and the fiow between the poles N2 and S2 is decreased, inducing a potential of opposite polarity in the coils and thus completing the full alternation. The coils being connected in series boosting (for vertical motion of the stylus) provide double the voltage of either single coil. As will be understood by those skilled in the art, the coils may be connected in parallel boosting, which will also result inthe currentalternations of the coils being in 7 phase for vertical movement of the stylus and 6. 180.. out of phase for: lateral; movement of the stylus. 1 ::i 'With the coils-connected as above described for vertical cut records, a. lateral ancillary force ap-i plied in the lateral direction,say to the right, will move the point 'of the stylus. 24 torthe right, causing the right side, of; armature I4 to rise and the. left side-to move downwardly an equal distance, which will produce a .change of flux in all of the arms or branches of the pole pieces, increasing the flow of flux from N I to S2 and-decreasing the flow of flux from'N2to ,SI, therebyinducing a poten tial'in' both of said coils. However, with the terminals connected as above noted, the potentials in the coils (resulting from lateral motion of the stylus) ware out. of phase orbucking, thereby.

resulting in zero voltage between the terminals 26a and 2111. Similarly, lateral movement of the stylus in the opposite direction will likewise result.

and 21b. v, y When the device isto be used in connection with lateral cut records the terminal 26b is connected to the terminal 2112 so that the poten-'-' tials due to l'ateralrmovement of the stylus are: additive or boosting; while the potentials result-. ing from ancillary vertical movement of the:

stylus are in bucking relationship and neutralize each other; Similarly, the coils may be con-- nested in parallel boosting forlateral motion of the stylus, by connecting terminals 26a and 21a to one branch vof the receiving circuit and terother. branch Of theiminals 26b and 21b to the receiving circuit.

four branches of the pole pieces in connection groove will actuate the stylus in both the vertical and lateral direction, i.- e., on -lateral cut records there are present ancillary vertical undulations and vice versa. Through the use of the-two coil arrangement the vertical scratch impulses are neutralized whenever the coils are connected for the reproduction of lateral cut records, and the lateral scratch impulses are neutralized whenever the coils are connected for the reproduction of vertical cut records.- This is a distinct advan- 'tage as it improves the ratio of amplitude of scratch noise to music. Additionally, the use of, two coils raises the efllciency of the pickup, and

therefore such use is greatly preferable.

Referring to Fig. 2, itis evident that whether flow is always from NI and N2 to-SI and S2; "and hence ther is no reversal of flow through the ;,armature Hi. When a vertical signal displaces the armature, either up or down, no substantial change in the quantity. ofvflux flow in thesaid armature takes place, as any decrease in flux cou-' pling between the armature and N2 and S2 results ;in an equal increase in flux coupling between N I and SI, the sum' total effect results in no variation in the said armature.

The term flux coupling is used toindicate that a variation in thequantity of flux now betwee? a lves. Pair p l s. 9 ierq a ir.

producing zero voltage between the terminals 26a- A single coil may: be used on any one of the the armature I4 moves in either a vertical direction or in a rocker fashion the direction of flux.

is obtained-by-varying the overleppingor inter-' leave area of armature coupling to said magnetic poles and not by the conventional reduction of the air: gap distancebetweenearmature and-pole;

For lateral reproduction, -the rocking motion or the armature-productions substantial change in the quantity or fluxflowing through the armature, forwhen the armature end adjacentpoles Ni and-NZ moves downward the saidflux con pllng. to N t decreasesthe same amount that it increasessin fiux coupling'to'Ni; the same conditiorr or course exists; between. the poles; St and-"S2, the sum total effectresultlngdnno flux variation,-

Because orthe absence of flux. reversals or variations, eddy currents and hysterisisl' do not exist, permitting a. densityof flux. in the armature that. imposes full saturation without. impairing. the fidelity of reproductiom This allows. the reduction of themasstott materialz-maki'ngit. possible to; extendthe rrequency range. In view or; this it is within the contemplation of theinvention to eliminate. the magnet M? (Fig. 1) and in its; place transformer iron can be substituted and thev armature then made 'of permanent; magnet. material; The fidelity will remainthe same the efficiency will be. in proportion to. the. strength 1 at the; magnet material used.

Further reductiorrof weight; in the armature is effected due to the fact that theefficiency is inno; way influenced by how longcrshort; the distance from- N1 and to; SI andaslmay be. It is:- therefore. desirable: tomake the width. and length or the; armature as; small as possible. Howeren.

the amplitude of the signal fromlateralrecordings dependsvupon-the ratid ofthe distance from thepoint of the stylus. (Fig. 1). to the. imagi nary center Cl-or rocking axis, toethe: distance from center C. to either end that. is adiacent the. poles Ni and Ni or Stand 82.. By, reducingthe, distance. of the stylus point, from the. axis-c to as short. a lengthas mechanical facilities allow, the. total length of the armature-can be brought to. where. the above mentioned ratio iseither 1. to 1: or a step. up'orstep downratioto suit application recruirements,,and have a total. armature. weightof direction of a. gram. Fig. 3 shows the; preferred relative proportions of.- the width of. the armature 1.4 toits length,

Havingthus described our invention; with. par ticularity: with referenceto a preferred. embodiment; thereof,, and having, referred to certain modifications, it. will-beobvious to those skilled. in the art, after understanding. our invention, that other changes andmodifications. may be made therein. without departing fromv the spirit and scopeof the. invention, andywe aim in the appended claims-to. cover such changes-and modiflcations as;- are-within the scope. of the. invention. What'we claim is:

1. In a pickup device of the magnetic type; the combination or a. magnetic circuit including poles of opposite polarity. and. having. parallel flux paths for each pole; each'oi said poles having upper and lower pole ends provided with. spaced vertical coplanar faces, a first. electrical coil surroundingone path of one pole'and. a second. electrical' coil'surrounding'a corresponding path of the opposite pole, said paths being so disposed with respect to each other as to provide parallel fields across which flux flows in the same lateral direction, and an armaturehaving laterally'op positely disposed ends provided. with vertical faces 5' having vertical surface areas disposed in spaced overlapping parallel relation with respectivelycorresponding vertical pole faces, .said armature. being supported about a laterally. central axis. with its oppositely disposed ends movable parallel to and-in continuoustflux coupling. relation with:

respectivehzv cooperating. faces: of said. pole faces. a: stylusisecured. to said armaturev for movement of said armature in said. field responsive to a. soundtrack record: throughout its range of move- ;ment, and a signal generatingc-ircuit; responsive.

tosaid armaturevibrations.

3. In. a. sound translation device of the magnetio type, magnet means having. pole pieces of. opposite: polarity each-having. upperand lower- -branches-provided with coplanar pole faces, an armature provided: with oppositely disposed endsadjacent respective pairs 01 said: branches of opposite polarity, said oppositely disposed. armature endssoverlapping said vertical pole. faces-inparallel spaced relation thcrewithsaid armature.

being supported for rockinemotion about; an axis: disposed intermediate said poles or opposite p0 larity in-a. lateral direction andintermediatesaid upper and. lower branches. in a'vertical direction.

:- spring means supporting said armature in a vertical position relative to saidpolebrancheswhcn in operative position and providing. for predetermined rocklng movement. about said. axis. in both directions and. providing. for predetermined vertical movement and restraining said; armature against bodily movement in a'latcral direction,

and. ancl'ectrical circuit. including a flux path through said armature.

4.. In a sound translation device of the masnetictype, the combination-of a plurality of pole pieces providing a pair of laterally disposed air aps spaced vertically one from theother, meansforsupplying magnetic flux across said air gaps in the. same direction of. flow, said pole pieces having vertical coplanar faces, an armature. in the field of. influence of said flux supported from its central point for rocking motion in a plane substantially. parallel to said coplanar pole faces about. an axis extending substantially normal to awthe direction of flux-flow across. said gaps; said stantially. vertical surface areas. movable parallel to andspaced'from respectively cooperating faces of said pole pieces, electricalcircuit'means including amagnetic flux fieldvariable synchro-- nously' with the movement of' said armature, anda mechanical motion translating elementattached tosaid armature;

5. Ina sound translationdevice'ofthe mag-- netlc type, the combination of magnetic pole' pieces of opposite polarity having spaced coplanar vertical side faces, an armature having verticalfaces in parallelism with the respective vertical faces of said pole pieces inspaced overlapping relationship therewith, and a support for said armature limiting movement of said vertical faces within a plane substantially parallel to the faces of said pole pieces. 6. In a sound translation device of the magnetic type; the combination of an armature sup ported for rocking-movement and for relatively vertical movement, a magnetic-circuit including poles of opposite polarity having laterally extending coplanar vertical pole faces of opposite polar ity providing a magnetic flux field within which said armature is movable in relatively 'opposite directions from a neutral positionysaid armature having vertical surface areas disposed in spaced overlapping parallel relation with respectively corresponding vertical pole faces, said armature being supported about a laterally central axis with its oppositely disposed ends movable parallel to and in continuous flux coupling relation with respectively cooperating faces of said pole faces, a stylus secured to said armature for movement with said armature throughout its said range of movement, and a'signal generating circuit 're-' sponsiveto movement of said armature.

7. In a sound translation device of the mag netic type; magnet means having pole pieces of opposite polarity-each having upper and lower branches, an armature provided with oppositely disposed ends adjacent respective pairsof said branches of opposite polarity, said ends and. respectively adjacent pole branchesbeing in spatial interleaved relationship providing clearance throughout the operating movement of said armature and providing relatively fixed air gaps and variable area coupling, said armature being supported for rocking motion about an axis disposed intermediate said poles of opposite polarity in a lateral direction and intermediate said upper and lower branche's'when'in operative position in a vertical direction, spring means for supporting sjaidarmature in a vertical position relative to said polar branches and providing for predeter; mined rocking movement about said axis in both directions and providing for pretermined vertical movement and restraining said armature against bodily movementin a lateral direction, and an electrical circuit including a flux path through said armature.

8. In a sound translation'device of themagnetic type, magnet means having pole pieces of opposite polarity each having upper and lower branches provided with coplanar vertical faces, an armature provided with oppositely disposed. ends adjacent respective pairs of said branches of opposite polarity, said oppositely disposed armature ends having vertical surface areas overlapping corresponding of said pole faces in parallel spaced relation therewith, spring means for supporting said armature in a vertical direction relative to said polar branches and providing for predetermined rocking movement about said axis in both directions and providing for predetermined vertical movement and restraining said armature against movement in a lateral direction, said spring means being of such compliance as to maintain said armature constantly in said overlapping parallel spaced relationship during the full range of its operative movement, and an electrical circuit comprising at least one coil surrounding one of said pole branches.

9. In a sound translation device of the magnetic type, magnet means having pole pieces of opposite polarity each having upper and lower branches provided with coplanar vertical faces, an armature mounted for bodily movement in an up and down direction and for rocking movement about an axis substantially normal to said first direction of movement and restrained against movement of said aXis laterally, said armature having oppositely, disposed ends provided with vertical surface areas spaced outwardly from said axis and. disposed adjacent respective pairs of said branches of opposite polarity in spaced overlapping parallelism with said vertical pole faces, spring means supporting said armature in a vertical direction relative to said polar branches when in operative position and providing for predetermined rocking movement about said axis in both directions and providing for predetermined vertical movement and restraining said armature against bodily movement in a lateral direction, and an electrical'circuit including a flux path through said armature.

10. In a device of the character described, the" combination of a magnetic circuit comprising pole members having pole ends of opposite polar ity spaced apart to provide a magnetic field, said pole ends having laterally extending coplanar vertical pole faces an armature disposed in said field and provided with a member rigidly secured thereto for movement therewith, said armature having vertical surfaces overlapping corresponding of said pole faces in spaced parallelism there with, stationary electrical coil means surrounding at least one of said pole members, and resilient means supporting said armature in continug, ous overlapping and substantially'constant spaced, parallel relationship with said pole'faces for prodetermined vibratile motion in a vertical dire'c tion and for predetermined rocking motion and restraining said armature against bodily lateral movement, whereby said armature is maintained in flux coupling relationship and its movement effects flux modulation by variable area coupling. 1

11. In a device of the character described, thef' combination of 'a'" magnetic circuit comprising; pole members having pole ends of opposite polar-f} ity spaced apartlto provide a magnetic field,'said"f pole ends having" laterally extending coplanar vertical pole faces an armature disposed insaidj field and provided with a member rigidly securedi' thereto for movement therewith, said armaturehaving vertical surfaces overlapping correspond-1 ing of said pole faces in spaced parallelism therewith, a plurality of stationary coils surrounding respective of saidpole members o f opposite polarity and providing means for supporting electrical alternations to areceiving circuit, said coils being connected in boosting relationship for vertical movements of said armature and in opposing relationship for rocking movements of said armature, and resilient means supporting said armature for predetermined vibratile motion in a vertical direction and. for predetermined rocking motion and restraining said armature against bodily lateral movement, whereby said armature is maintained in flux coupling relationship and its movement effects flux modulation by variable 11 ai P e V faces in vspa ed;.i 2=i a 1I -ism t e ewith.- -;Dhl alityV0 tation yfi i fi l i l nm res e tive of said pole mei nbers or opposite polarityand v gk a r o si nl insiel ca a te nations toa receiving circuit, saidrcoils being connected in boosting relationship ior rocking movementsof said armature and in opposing relationship for vertical movements of said armature, a e e tme ns sunpo tins s id. erma' li l continuous ov l pin and sub antially nstani'. spaced parallel relationship with said p ole amazes faces or p ede er ned .vibratfl m ti n n L 7 vertical direction and for predetermined rocking motion and rest in n eid {a m tu e a ains fl l e a .m v men wh r b sa d armatur is maintained in flux coupling relaltions'hip and itsjmovement effects flux modulation by variable areav coupling.

13. In a, magnetic type pickup, ft-hecombination 01' a magnetic circuit including laterallvspaced pole ends of opposite polarity having laterally extending vertical pole face areas arranged in coplanar r at ns ip and p o d a Zfiu vfiel including a laterally extending 1. air p disposed between spacedpole ends or opposite polarity. .a A

vibratory armaturedisposedin saidl'fiux field and having substantially vertical 7 face areas extendingin substantialspaeed parallelism to and overlapping said pole faces a stylus rigidlysecured'to a a m t re i i ntsup rtme m ansiorsa d armature, whereby upon movementof said stylus by s a vertical cut record said armature is moved relative tosaid pole ends 'ina direction (tran verse to said flux :flow while mainta ned in said su sta i l p ll l sm and said armature rmd a movab na l l to es ively coope in faces of said pole ends.

+1- 1. am n ti t p picku h tc mb na of gm eneti circu lharin qnposi e ycd sn se pole niece P vide with substant al y vert c laterall ext ndin c lana po i e mct d and j i n sed s a t pr i w a eapflux paths across bot or h ch fluX l ws:i e am 'later l direc nnanslspace apart in v e tively v rtic rection. anearmatu e h ing vertical face areas disposed in spaced parallel relationship with respectively corresponding of said pole faces, resilient means supporting said armature for differential movement relative to said flux 'streams in overlapping 'relations'hipwith said coplanar-pole faces whereby when said devicejis in operative position said armature iies in the path of "both iiux's'tream and rsdisposedin flux coupling relationship "to said pole pieces th hou its ra i in v ent.

endsa arm tur nds movable para el-at r sp ct ly enum ra i face ofise p e ends- 15. In nn agnetic pickup the combination-of; magnetic circuit providinga flux fleldinclud-ing two spaced flux streams flowing ina lateral direct on c o s a airis pr defined p d s ns s tial y ve ca ccop a pole a es a vibratory armature jhaving substantially vertical a all oppo ely disposedlface a e ss ylus ri ly se ed t s id armature. nd esil n means ndepen ent o a dp ae d s por n said ;.armat1ire inoperative neutral position with said IBJZIDSJAHBdiSQOSBdiH said flux field-in substantiailly magnetic -equi1ibrium relative to said fluxs ams se r a ea aced closely adiacent and in substantially parallel overlapni g relationship \with;.corresponding of said coplanar pole faces, saidresilientsupporting means guiding said armature during its .vihratile movement and maintaining ,said spaced and substantially parallel overlapping relationship throughout the operative movementofsaid arma-.

ture, whereby saidfiiix is modulatedhyrvariable area co pling, and an electrical circuit responsive to said flux modulation.

LIONELB. CORNWELL. JOHN NIELSEN.

REFE ENCE TQI E 'lhe iollowing ref erencesrare' of record ii n the file of this ;patent:

UNITED STATES PATENTS 

